US 12,221,421 B2
Process for synthesis of Fipronil
Keki Hormusji Gharda, Maharashtra (IN); Diwakar Shenoy, Maharashtra (IN); Laxminarayan Shet, Maharashtra (IN); Yatin Samangadkar, Maharashtra (IN); and Abhijeet Suresh Kawade, Maharashtra (IN)
Assigned to GHARDA CHEMICALS LIMITED, Maharashtra (IN)
Appl. No. 17/439,870
Filed by Gharda Chemicals Limited, Maharashtra (IN)
PCT Filed Feb. 24, 2020, PCT No. PCT/IB2020/051532
§ 371(c)(1), (2) Date Sep. 16, 2021,
PCT Pub. No. WO2020/188376, PCT Pub. Date Sep. 24, 2020.
Claims priority of application No. 201921010712 (IN), filed on Mar. 19, 2019.
Prior Publication US 2022/0185783 A1, Jun. 16, 2022
Int. Cl. C07D 231/44 (2006.01)
CPC C07D 231/44 (2013.01) 18 Claims
 
1. A process for the synthesis of fipronil, the process comprising the following steps:
a) reacting trifluoromethane sulfinyl chloride with 5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-pyrazole and amine hydrochloride in a halogenated fluid medium to obtain a reaction mixture;
b) cooling said reaction mixture to a temperature in the range of 20° C. to 35° C. to obtain a cooled reaction mixture;
c) adding a mixture of said halogenated fluid medium and water to said cooled reaction mixture to obtain an admixture;
d) neutralizing said admixture with a neutralizing agent to obtain a biphasic mixture containing an organic phase and an aqueous phase;
e) separating said organic phase comprising fipronil followed by cooling said separated organic phase to a temperature in the range of 2° C. to 30° C. to obtain a precipitate of fipronil; and
f) filtering said precipitate to obtain a solid, washing said solid and drying said washed solid to obtain fipronil with purity in the range of 95% to 97%;
wherein the amount of 5-amino-1-(2,6-dichloro-4-trifluoromethylphenyl)-3-cyano-4-trifluoromethylsulfonyl pyrazole in the fipronil is in the range of 0% to 0.5%.